Genetic Disorders
Overview
Most of what your genes do passes unnoticed. Occasionally a single faulty version of one gene, or one chromosome too many, produces an effect large enough to shape a whole life. These are the genetic disorders, and they are among the few places in biology where a family tree, a fraction and a set of symptoms all describe the same thing. Learn to move between those three descriptions and this topic becomes arithmetic rather than memory.
In this lesson you will meet three inherited conditions that the specification names by example, and you will see why one of them shows up in every generation of a family while another can hide for decades in people who feel completely well. You will then look at a different kind of cause altogether, where nothing is wrong with any individual allele and the problem is simply that a cell finished up with the wrong number of chromosomes. By the end you will be able to read a family diagram, fill a Punnett square, quote a probability and explain the biology sitting behind the number.
Objectives
- Attention is drawn to the potential sensitivity needed in teaching about inherited disorders.
- Some disorders are inherited. Students should be able to interpret data relating to genetic disorders such as polydactyly, cystic fibrosis, and sickle cell anaemia.
- Some inherited conditions are caused by inheritance of abnormal numbers of chromosomes, eg Down’s Syndrome is caused by the presence of an extra chromosome.
Mind map
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Genetic Disorders. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Cystic fibrosis is caused by a recessive allele f. The working allele is F. What is the genotype of a carrier of cystic fibrosis? A. FF B. Ff C. ff D. A carrier has no alleles for the gene Answer: B
- Polydactyly is caused by a dominant allele. Which statement is correct? A. A person needs two copies of the allele to have the condition B. A person with one copy of the allele has the condition C. The condition always skips a generation D. Only females can have the condition Answer: B
- How many chromosomes are found in a body cell of a person with Down's syndrome? A. 23 B. 45 C. 46 D. 47 Answer: D
- Two carriers of cystic fibrosis have a child. What is the percentage chance that the child has cystic fibrosis? A. 0% B. 25% C. 50% D. 75% Answer: B
- Which of the following describes the event that leads to Down's syndrome? A. A dominant allele is inherited from one parent B. A recessive allele is inherited from both parents C. A pair of chromosomes fails to separate during meiosis D. A chromosome is lost during mitosis in the adult Answer: C
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